fix: allow assertUrlIs() to accept path-only notation

[delabon]

Previously, assertUrlIs() only accepted full URLs because it matched against the complete URL including scheme, host, and port.

This made tests like ->assertUrlIs('/login') fail even when the browser was on the correct path.

Now the function intelligently detects whether the input is a full URL or just a path:

• If input contains a scheme (e.g., http://), matches full URL
• If input is just a path (e.g., /login), matches only the path portion

This change maintains backward compatibility while adding the expected convenience of path-only assertions.

Reported by pestphp/pest#1607